Excavator steering mechanism

ABSTRACT

A steering mechanism steers in pairs the four dual crawler trucks of a strip mining shovel by diagonally mounting steering members between the two dual crawler trucks of each pair. In the first embodiment two powered double acting cylinders are diagonally end mounted in tandem to form each of the steering members. The second embodiment employs a pair of diagonally end mounted hydraulic rams. In a third embodiment each of the steering members is a pair of racks driven by a common pinion. In a fourth embodiment, a pair of cylinders mounting worm gears and having screws telescoped within them are diagonally mounted between a pair of dual crawler trucks.

Unite States Patent 91 Talley [54] EXCAVATOR STEERING MECHANISM [75 Inventor: Robert E. Talley, Racine, Wis.

[73] Assignee: Bucyrus-Erie Company, South Milwaukee, Wis.

[22] Filed: Aug. 6, 1971 [21] Appl. No.: 169,748

52 us. Cl. ..1s0/9.44, 280/96 [51] Int. Cl. ..B62d 7/14 [58] Field of Search ..180/9.44, 79.2 R, 180/79.2 C, 9.46, 24.01, 50, 44, 45, 46; 305/44 [56] References Cited UNITED STATES PATENTS 1,804,816 5/1931 Shelton ..180/9.46 2,360,902 10/1944 Simmons ...280/406 R Schroeder.... ..180/79.2 R Gleasman ..180/79.2 R

4/1971 Sipos ..74/99 3,650,343 3/1972 Helsell 1 80/50 X Primary Examiner-Kenneth H. Betts Assistant Examiner-Reinhard Eisenzopf Attorney-Thomas O. Kloehn, Arthur H. Seidel and John A. Thierry [57 ABSTRACT A steering mechanism steers in pairs the four dual crawler trucks of a strip mining shovel by diagonally mounting steering members between the two dual crawler trucks of each pair. In the first embodiment two powered double acting cylinders are diagonally end mounted in tandem to form each of the steering members. The second embodiment employs a pair of diagonallyend mounted hydraulic rams. In a third em bodiment each of the steering members is a pair of racks driven by a common pinion. In a fourth embodiment, a pair of cylinders mounting worm gears and having screws telescoped within them are diagonally mounted between a pair of dual crawler trucks.

3 Claims, Drawing Figures PATENTEB MAY 2 9I97 5 SHEET 1 [1F 4 INVENTOR ROBERT E. TALLEY ATTORNEY PATENTEDMY29I9Y5 3.735.829

SHEET 2 OF A INVENTOR ROBERT E. TALLEY ATTORNEY PATENTEB MAY 2 9 I975 SHEET 3 BF 4 INVENTOR RQBERT E.TALLEY BY p ATTORNEY PATENTED 8,735,823

SHEET k$ [1F Q INVENTOR ROBERT E. TALLEY ATTORNEY 1 EXCAVATOR STEERING MECHANISM BACKGROUND OF THE INVENTION The present invention was created as a new type of steering mechanism for the huge strip mining shovels which move hundreds of feet of overburden to expose deeply buried seams of coal for mining. Such huge shovels are being developed with ever increasing dipper capacity and length of reach to allow open mining to replace tunnel miningof deeper veins of coal. Shovels of this sort are described in US. Pat. No. 3,376,983, and No. 3,258,143. The sizes and capacitiesof these shovels defy imagination, and create problems which are virtually unique to these machines.

A recitation of some of the specifications of a stripping shovel for which the present'invention is initially intended may help to illustrate the problems. The revolving frame clears the ground by 33 feet and is supported on four dual crawler type trucks with a tread of 63 6 feet, each crawler being -6 k feet wide. The length of the mounting, which in autos is called the wheelbase, is 79 feet. Each dual crawler truck is driven by a pair of 200 horsepower engines. The boom foot pin on top of the revolving frame is 40 feet above ground, and the boom itself is 170 feet long. The dipper has a capacity or 130 cubic yards, a maximum dumping height of 117 /z feet, and a maximum dumping radius of 163 feet. The weight of this stripping shovel is 13,700,000 thousand pounds. Similar shovels enlarged to provide dippers with over 200 cubic yards capacity are in planning.

At the present, the steering of power shovels of this sort is accomplished by two single acting rams to pivot a pair of dual crawler trucks. The 'rams are each end mounted between the inside end of one of the crawler I truck. A tie rod pins the trucks that form a pair so that both trucks move together. Although this type of steermg system provides ample steering control it has inherent problems which primarily result from the manner in which these shovels are utilized, the severity t which increases abruptly with the enlargement 0t these machines. Such shovels are operatedas near to the base of the material being dug as possible, but the operators should take care not to allow overburden from falling down among the crawler trucks. However, increasing the distance of the shovel from the base of the material to be dug reduces the depth of overburden that the shovel can dig because the depth of overburden that can be removed is a function of the effective reach of the shovel. Since the cost of these shovels increases with its size', the natural motivation of the mine owner is to purchase the smallest possible machine and operate it as close as possible to the bank so as to maximize its effective reach. When the shovel is operated more to the bank than is recommended, the overburden piles up against the crawler trucks of the machine. Consequently, when the machine is moved and the trucks are turned, the steering mechanism must drive the crawlers into the bank of overburden, imposing extremely high stresses on the entire undercarriage assembly. In one size machine, for example, the steering mechanism exerts up to 400,000 pounds of steering force on each dual crawler truck. Due to the disposition of the hydraulic cylinders between the crawler trucks and the strut depending from the shovel base,

the large stresses from the steering forces are transmitted to the frame of the shovel, where they become entrapped and finally find release in buckling of the frame itself.

The present invention provides a steering mechanism that substantially reduces the danger of locked in stress forces in the shovel frame through the positioning of the crawler truck steering members between two crawler trucks in such fashion that the application of a steering force on one of the crawler trucks is counteracted by the application of an equal and opposite force that is directed against the other of the two trucks. One important effect of the exertion of steering forces in such a system is the elimination of any significant locked in forces from the shovel frame. Instead, the force expended in steering the crawler trucks is primarily restricted to the trucks, and buckling of the frame due to locked in steering stress is avoided.

SUMMARY OF THE INVENTION The present invention relates to the steering mechanism for the crawler trucks of large strip mining shovels and more specifically, the invention resides in two steering members that are diagonally oriented to one another and are disposed between a pair of crawler trucks to control the steering of said pair of trucks.

chines capable-of eliminating the transmission of all significant steering stress forces to the machine frame; and

To provide a steering mechanism for a crawler driven machine that obviates locked in stresses in the machine frame which derive from the steering forces.

The following portion of this specification in conjunction with the attached drawing provides a written description of the present invention and of the manner of using it in such clear, full, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected to make and use the same. In addition, preferred embodiments of the invention are disclosed in detail in order to set forth the best modes contemplated by the inventor for carrying out the invention. However, the specific embodiment of the invention disclosed here does not attemptto represent the full scope of the invention. On the contrary, the invention may be employed in many different embodiments. Therefore, the conclusion of the descriptive portion of this specification, the subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in numbered claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial front view in elevation of a power shovel employing a first embodiment of the steering mechanism of the present invention with the revolving frame of the shovel rotated toward one side,

FIG. 2 is a plan view schematic representation of a front and a rear pair of dual crawler trucks of the power shovel of FIG. 1 with a first embodiment of the steering mechanism of the present invention connected interjacent the crawler trucks of each pair,

FIG. 3 is a plan view schematic representation of the front pair of crawler trucks of FIG. 2 with a second embodiment of the present invention connected therebetween,

FIG. 4 is a plan view schematic representation of the crawler trucks of FIG. 3 with a third embodiment of the present invention connected therebetween,

FIG. is a plan view schematic representation of the crawler trucks of FIG. 3 with a fourth embodiment of the present invention connected therebetween,

, FIG. 6 is a fragmentary side view of a steering member of the fourth embodiment of FIG. 5,

FIG. 7 is a schematic representation of the first embodiment as illustrated in FIG. 2 and including the hydraulic system that controls said embodiment, and

FIG. 8 is a schematic representation of the second embodiment as illustrated in FIG. 3 and including the hydraulic system that controls said embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT The power shovel shown in FIG. 1 is built around a revolving frame 1 which is rotatably mounted on a base 2. Two front crawler type trucks 3 and 4 that support the shovel in conjunction with two rear crawler trucks 5 and 6 may be seen mounting the base 2, under each corner, by means of an automatically leveling suspension system utilizing hydraulic jacks 7 and the trucks 3-6 act as running supports for movement across terrain. The revolving frame 1 supports a large machine housing 8 containing the drive motors and associated mechanism (not shown) for operating the shovel in addition to providing a foundation for a superstructure.

The superstructure of the shovel is partially shown in FIG. 1. A complete illustration of the superstructure and a detailed description of its elements is described in U.S. Pat. No. 3,258,143. The superstructure is mounted on the revolving frame 1 and includes a vertically rising A-frame 9 and a bottom 10 which angles forward and upward from its pivotal mounting at the front end of the revolving frame 1. Boom support cables (not shown) are strung from the top of the boom 10 to the top of the A-frame 9 to support the top of the boom 10.

FIG. 2 illustrates the placement of the four crawler type trucks 3, 4, 5 and 6 with respect to one another, a front pair 3 and 4, and a rear pair 5 and 6. Each of the crawler trucks 3, 4, 5 and 6 is composed of a composite welded and cast steel frame 11 and the loads from the base 2 are transmitted to the trucks 3, 4, 5 and 6 through the hydraulic jacks 7. On each side of the truck frame 11 is a track 12 of wide face, long pitch, cast links (not shown) of heat treated steel, which are connected by special steel pins (not shown). Each of the trucks 3, 4, 5 and 6 is driven by its own driving motor (not shown) which is mounted atop the truck frame 11. The trucks 3 and 4 that form the front truck pair are connected together by a first embodiment of the present invention and the rear pair of trucks 5 and 6 are connected together in a similar fashion. For purposes of simplicity and clarity, only the components of the present invention that connect between the trucks 3 and 4 will be specifically described, but it should be kept in mind that the components that connect between the trucks 5 and 6 are similarly structured and are indicated by primed numbers of their corresponding elements.

The embodiment of FIG. 2 is comprised of four double acting hydraulic cylinders 13, 14, 15 and 16, which each have a blind end 17 that is pivotally attached to one corner of a square center bracket 18 suspended from the bottom of the base 2 to serve as a coupling means. The cylinders 13, 14, 15 and 16 are each made up of a cylindrical bore 19 in which a piston 20 is reciprocally mounted. An outer end 21 of a piston rod 22 extends axially from one end of the piston 20 through a rod end 23 of the cylindrical bore 19. The outer rod ends 21 of each of the cylinders 13, 14, 15 and 16 are adapted to be pivotally and rotatably connected by connecting means, which are shown as pins A, to an inside comer of one of the trucks 3 or 4. When the blind ends 17 and piston rod ends 21 of the cylinders 13, 14, 15 and 16 are connected in this manner, two of the cylinders 13 and 14 connected in tandem by the center bracket 18 operatively form a first steering member 24, and the two remaining cylinders 15 and 16, which are also connected in tandem by the center bracket 18, operatively form a second steering member 25 that is diagonally oriented to the steering member 24.

To control the steering of the trucks 3 and 4 the two steering members 24 and 25 act in unison. To turn the trucks 3 and 4 in a counterclockwise direction the two cylinders 13 and 14 comprising the steering member 24 are extended while the two cylinders 15 and 16 comprising the steering member 25 are retracted. The effect of this action is to extend the steering member 24 while at the same time retract the steering member 25.

I-Ience, the trucks 3 and 4 are forced to turn in a clockwise direction commensurately with the extension and retraction of the steering members 24 and 25. To turn the trucks 3 and 4 in a clockwise direction, steering member 25 must be extended and steering member 24 must be retracted. Although the cylinders 13, 14, 15 and 16 are conventional, hydraulically powered, double acting cylinders, electric cylinders and linear magnetic motors are also known that could perform in the same manner.

There are various hydraulic circuits that would serve to control the steering members 24 and 25 to steer the front pair of trucks 3 and 4 and in addition control a second pair of steering members for the rear pair of trucks 5 and 6. FIG. 7 illustrates one such type of hydraulic system. For simplicity and clarity only that portion of the hydraulic circuit that controls the steering members 24 and 25 will be described as the opposite portion of the system functions in an identical manner and the elements of the opposite portion have primed numbers that correspond to the numbers of the similar elements in the portion described. An electric motor 26 furnishes power to a hydraulic pump 27 that pumps hydraulic fluid out of the system fluid reservoir 28. This fluid is pumped into a working line 29 that leads to a four connection, four-way valve 30. A relief valve 31 is connected to the working line 29 between the pump 27 and the four-way valve 30 to control maximum pressure in the working line 29. Actuation of the four-way valve 30 determines how and when hydraulic fluid will be supplied to the cylinders l3, 14, 15 and 16. Leading from the four-way valve 30 are two working lines 32 and 33 that provide communication between the fourway valve 30 and the hydraulic cylinders l3, 14, 15 and 16. The lines 32 and 33 alternately serve as a supply line to supply fluid to the cylinders 13, 14, 15 and 16 and as a first return line that returns fluid from the cylinders 13, 14, 15 and 16 back to the four-way valve 30. A second return line 34 connects the four-way valve 30 and the reservoir 28. When the four-way valve 30 is in a neutral position the main working line 29 and the second return line 34 are blocked. Therefore, no fluid enters or exits from the cylinders 13, 14, 15 and 16 and there is no movement of the cylinder pistons 20. When the valve 30 is actuated in a first operating position the line 32 supplies fluid to the blind ends 17 of the cylinders 13 and 14' that comprise the steering member 24 and the increase in fluid pressure forces the pistons 20 towards the rod ends 23 of the bores 19 thus extending the piston rods 22 to lengthen the steering member 24. During this movement of the pistons 20 in the cylinders 13 and 14, fluid is forced out of their rod ends 23 into the line 33 to be conveyed back to the reservoir 28 through the valve 30 and the second return line 34. At the same time, fluid is fed from the line 32 to the rod ends 23 of the cylinders 15 and 16 that comprise the steering member 25. The increase in fluid pressure in these rod ends 23 causes their pistons 20 to move toward the cylinder blind ends 17. This movement of the pistons 20 forces fluid out of the blind ends 17 of the cylinders 15 and 16 to return to the reservoir 28, thus, retracting the piston rods 22 of the cylinders 15 and 16 and shortening the steering member 25. By actuating the valve 30 in a'second operating position the aforementioned manner in which the fluid is supplied and removed from the cylinders 13, 14, 15 and 16 is reversed, hence, the steeringmember 24 is shortened and the steering member 25 is lengthened resulting in turning the trucks 3 and 4 in a counterclockwise direction. When the trucks 3 and 4 of the shovel are turned as described above to cause the shovel to travel along a circular path, a tie rod 35 as shown in FIG. 2, which is pivotally connected to the rear portions of the two trucks 3 and 4 and precisely spaced from the jacks 7 a calculated distance, causes the truck 3 or 4 which'is nearest the center of the turning circle to be turned through a larger angle than the truck 3 or 4 that is more remote from the center to provide what is commonly referred-to as an Ackerman correction." If this relationship is not established during circular travel of the shovel, one of the trucks 3 or 4 will not be turned in the direction of the arc of movement, creating extreme stresses when that truck 3 or 4 is forced to slide transversely to the direction of travel.

The embodiment of FIG. 3 is quite similar to the embodiment of FIG. 2 except that single rarns alone comprise steering members 36 and 37 respectively. As illustrated in FIG. 3 the steering members 36 and 37 each have a piston rod 38 and a blind end 39. An outer end 40 of the rod 38 and the blind end 39 of each steering member 36 and 37 are pivotally connected as by pins B to one of two trucks 41 or 42 which comprise a front pair of trucks. The steering member 37 has its piston rod outer end 40 connected to the inside forward end of the truck 41 and its blind end 39 is pivotally connected to the inside rearward end of the truck 42. The steering member 36 has its piston rod outer end 40 pivotally connected to the inside forward end of the truck 41 and its blind end 39 is pivotally connected to the inside forward end of the truck 42 to diagonally cross over the steering member 36. In this embodiment, it can clearly be seen that by extending the steering member 37 and retracting the steering member 36 the trucks 41 and 42 will be rotated in a clockwise direction, a proportionate distance to the extension and retraction of the steering members 37 and 36 respectively. In similar fashion, if the steering member 36 io extended while the steering member 37 is retracted the trucks 41 and 42 will rotate in a counterclockwise direction for a distance proportionate to the extension and retraction of the two steering members 36 and 37 respectively. In this embodiment, just as in the first embodiment, a tie rod 43 is pivotally connected between the trucks 41 and 42 to provide the Ackerman correction.

FIG. 3 is a schematic diagram illustrating one type of hydraulic system that would adequately control the second embodiment of the steering mechanism that is connected between the front pair of trucks 41 and 42 and between a rear pair of trucks (not shown). Again, for simplicity, only that portion of the hydraulic circuit that controls .the front steering mechanism will be described and similar elements for the rear pair of trucks are indicated with primed numbers. Similar to the hydraulic circuit of FIG. 7, there is an electric motor 44 that drives a fluid pump 45 supplying hydraulic fluid to a working line 46 from a reservoir 47. The working line 46 leads to a four-way valve 43. Connected to the line 46 between the four-way valve 48 and the fluid pump 45 is a relief valve 49 that controls the maximum pres sure in the working line 46. Leading from the four-way valve 48 are two working lines 50 and 51 that provide communication between the four-way valve 46 and the steering members 36 and 37. The lines 50 and 51 alternately serve as a supply line to supply fluid to one of the steering members 36 or 37 and as a first return line that returns fluid from one of the steering members 36 or 37 to the four-way valve 48. A second return line 52 connects the four-way valve 46 to the reservoir 47. When the four-way valve 48 is in a neutral position, the working line 46 and the second return line 52 are blocked by the four-way valve 48, hence, no fluid is supplied to either of the steering members 36 or 37, nor is fluid returned from either steering member 36 or 37 back to the reservoir 47. The steering members 36 and 37 are each comprised of a cylindrical bore 53 in which a piston 54 is reciprocally mounted. The piston rods 33 of each steering member 36 and 37 extend axially from one end of pistons 54 through rod ends 55 of the cylin-' drical bore 53. In a first non-neutral position the line 50 supplies fluid to the blind end 39 of the steering member 36 to cause its extension. Concurrently, the line 51 receives fluid from the blind end 39 of the steering member 37 and conveys it back to the reservoir 47 via the four-way valve 48 and the line 52, which results in retraction of the steering member 37. In a second nonneutral position, the line 51 supplies fluid to the steering member 37 and the line 50 conveys fluid away from the steering member 36, which results in the aforementioned fluid flow being reversed. Hence, steering member 37 is extended, causing steering member 36 to retract.

The principal aspect of the present invention is the steering of a pair of crawler trucks through the employment of a pair of diagonally oriented steering members and there are many other structures than those described above that may be used to form such steering members. FIG. 4 illustrates a third embodiment of the present invention which utilizes steering members 37 and 58 each comprised of a cylindrical bore 59 in which a rod 60 resides. Worm threads 61 are cut in the rods 60 to mesh with wormgears 62 that may be powered by any appropriate power source to extend and retract the steering member rods 60. In this embodiment, again the extension of the steering member 57 during retraction of the steering member 58 and vice versa, produces the steering of crawler trucks 63 and 64 and a tie rod 65 is pivotally connected between the trucks 63 and 64 to provide the Ackerman correction.

FIG. illustrates a fourth embodiment of the present invention that substitutes a rack and pinion movement in steering members 66 and 67 for the screw and worm movement of the third embodiment. The steering members 66 and 67 are disposed between the trucks 68 and 69. As shown in FIG. 6 the members 66 and 67 are comprised of two parallel racks 70 spaced apart a sufficient distance for a pinion 71 to be disposed between them in such manner that the pinion 71 engages teeth 72 of each of the racks 70. The racks 70 are slidably held together by a sleeve 73 on top of which sets an electric motor 74 that powers the pinion 70. There are two support struts 75 connected to opposite sides of the sleeve 73 and the struts 75 extend upward and are affixed to the bottom of the base 2 to aid in the support of the steering members 66 and 67. The sleeve 73 contains two springs 76 that provide a certain amount of downward tension on the upper rack 70 in order that the pinion 71 will be tightly held together between the two racks 70 without becoming jammed between them. To provide the Ackerman correction for the trucks 68 and 69 a tie rod 77 is bridged between them.

The embodiments of the invention shown and described herein provide an improved steering mechanism for the supporting trucks of large strip mining shovels to substantially lessen the stress forces in their frames as they are steered.

Although preferred embodiments of the invention have been shown, it will be obvious that various modifications are possible withoutdeparture from the spirit of the'invention. The invention is of course not limited 1 in use with excavator shovels but may be advantageously utilized with various types of vehicles having running supports that require a large amount of steering force.

I claim:

1. A steering mechanism for steering running supports movably supporting a frame of a vehicle, said steering mechanism comprising the combination of a pair of running supports supporting a vehicle for movement across terrain, said running supports being mounted on a vehicle frame for independent pivotal movement about spaced apart substantially vertical axes; connecting means secured to said pair of running supports, said connecting means on each of said running supports being located respectively both forwardly and rearwardly of said substantially vertical axes; pair of steering members diagonally oriented to cross one another and to connect said rearwardly located connecting means on one of said running supports with said forwardly located connecting means of another of said running supports each of said steering members including two longitudinally extendable and retractable units linked together at one end in tandem to operate simultaneously to extend or retract the respective steering member; and drive means being connected directly to the units of at least one of said steering members to extend and retract said steering member. 2. A steering mechanism as set forth in claim 1 wherein:

said units of both steering members are linked together by a coupling means suspended from the base of the vehicle;

said units connected to said drive means are hydraulic cylinders; and said drive means is a hydraulic fluid system connected to supply fluid under pressure to said hydraulic cylinders.

3. A steering mechanism as set forth in claim 2 wherein said hydraulic cylinders are double acting hydraulic cylinders. 

1. A steering mechanism for steering running supports movably supporting a frame of a vehicle, said steering mechanism comprising the combination of a pair of running supports supporting a vehicle for movement across terrain, said running supports being mounted on a vehicle frame for independent pivotal movement about spaced apart substantially vertical axes; connecting means secured to said pair of running supports, said connecting means on each of said running supports being located respectively both forwardly and rearwardly of said substantially vertical axes; a pair of steering members diagonally oriented to cross one another and to connect said rearwardly located connecting means on one of said running supports with said forwardly located connecting means of another of said running supports each of said steering members including two longitudinally extendable and retractable units linked together at one end in tandem to operate simultaneously to extend or retract the respective steering member; and drive means being connected directly to the units of at least one of said steering members to extend and retract said steering member.
 2. A steering mechanism as set forth in claim 1 wherein: said units of both steering members are linked together by a coupling means suspended from the base of the vehicle; said units connected to said drive means are hydraulic cylinders; and said drive means is a hydraulic fluid system connected to supply fluid under pressure to said hydraulic cylinders.
 3. A steering mechanism as set forth in claim 2 wherein said hydraulic cylinders are double acting hydraulic cylinders. 